(a) Field of the Invention
The present invention relates generally to a method of making ball valves, and more particularly to a method in which two symmetrical ball valve halves are forged into shape and are welded together using friction welding such that a hollow spherical ball valve with a straight flow channel in the center is accomplished. Ribs formed on the welding surfaces at the straight flow path are removed by punching to achieve smooth surfaces. The surface of the ball valve is finally processed to achieve a weight-reduced ball valve. In use, the load borne by the water stopping washers on both sides of the ball valve can be reduced to prolong the service life of the water stopping washers. Besides, the straight flow channel allows smooth flow of water therethrough; the ball valve has good structural strength; and manufacturing costs can be lowered.
(b) Description of the Prior Art
The ball valve referred to herein is, as shown in FIG. 1, a ball valve structure that rests against water stopping washers 51 of a water valve and rotates to control the opening and closing of a water faucet. Referring to FIG. 2, in the past, ball valves were made by casting. Cast iron is poured in a mold, and a ball-shaped semi-finished product is removed from the mold after drying. The surface thereof is then processed and burred to accomplish a ball valve product.
However, there are many disadvantages with a ball valve made in the above-described method.
1. As the conventional ball valve is formed by casting, there are air bubbles inside during casting. During formation, in order to reduce the number of pores formed on the surface of the ball valve, the thickness of the ball valve is increased deliberately. After formation, the surface layer is processed using a lathe. It can be seen that proportion of waste material is high, yet there are still pores on the surface of the ball valve. As a result, the surface of the ball valve is not in tight fit with the water stopping washers on both sides of the water hole of the faucet, and water leaks through the pores of the ball valve. It can therefore be seen that it is impossible to form a ball vale free of pores using such a casting method. PA0 2. Furthermore, the conventional ball valve has a substantially spherical hollow interior (as shown in FIG. 2). When water from the water hole of the faucet flows through the hollow interior of the ball valve, it will hit against the walls of the substantially spherical hollow interior of the ball valve so that air bubbles are formed in the piping. These air bubbles obstruct the smooth flowing of liquid, thereby causing the formation of turbulence.
In order to overcome the above-described drawbacks, forging is adopted make ball valves. Referring to FIG. 3, a steel material is heated at high temperature and forged directly into a solid spherical semi-finished product. After surface processing, a ball valve structure 3 is accomplished.
However, although making ball valves using forging can eliminate the disadvantages of the cast ball valves, there are other problems to be solved.
Since a solid ball valve is heavy, when the ball valve urges against the water stopping washers 51 of the water valve 5 and rotates, the weight of the ball valve on the water stopping washers (since both side portions of the ball valve are inserted into the water stopping washers) will cause the water stopping washers to deform in shape after a period of time, and they will also become vulnerable to wear during rotation of the ball valve. As a result of deformation and wear, the ball valve can no longer be in tight fit with the water stopping washers on both sides, and clearances are formed. Therefore, even when the ball valve closes, there is leakage in the piping. And when a technician come to maintain the piping by employing welding, explosion may easily occur.